Wanted to share the circuit and also the method of construction for the lighting enclosure which worked out quiet well.
There are many variations that one could make here. With a higher voltage battery pack, the circuit will drive at least 2 more LEDs (6 in total) or less could be used. Different optics or mountings could also be used.
As there is already quiet a detailed work log on NoBMoB please check there: Rob's Homemade LEDs.
Have just included a couple of brief steps, please visit the above for the details.
Step 1: Circuit Design
The circuit below uses rudimentary logic to turn of the main LEDs with the simple flasher and 'low' battery warning - in effect this 'blinks' the main LEDs when the battery is getting low.
A second voltage comparison turns of the main LEDs when the battery pack voltage is getting too low, to prevent over-discharge. What's good here is that in doing so raises the input voltage and we get a feedback loop that actually causes the main LEDs to dim nicely rather than cut out abruptly.
Step 2: Construct Circuit
Mount the finished PCB inside your enclosure.
Step 3: Cut, Bend, Drill
Step 4: Finish LED Housings
Mount to aluminium angle with heat sinks behind as shown.